The name derives from the Italian verb migliorare (to improve), because its main goal was to improve the Italian capitalist system from the inside, by means of gradual reforms, according to a social democratic policy, rather than full-scale revolution. Its origins lay in the ideas of Giorgio Amendola, a prominent MP and member of the communist party during the period post-World War II, who thought about gradually abandoning Marxism in order to embrace social democratic and reformist theories. These ideas were suited to making alliances with more moderate left-wing parties, such as the Italian Socialist Party and the Italian Social Democratic Party.

Meliorism received extensive derogatory treatment from the left wing of the Communist Party, headed by Pietro Ingrao. They received some modest support from the pro-Soviet wing of the party, headed by Armando Cossutta.

During the 80s there were frequent conflicts between the secretary of the Communist Party Enrico Berlinguer and the meliorists, the latter criticizing Berlinguer's renunciation of the historic compromise and his hostility to Bettino Craxi. They believed that the party was leaving to Craxi's Italian Socialist Party the monopoly of modernity in politics, failing to acknowledge the changes that had occurred in Italy. According to some critics, Bettino Craxi, the head of the PSI, used the meliorist wing as a tool to hamper Berlinguer.

During Tangentopoli the meliorist wing of the Democratic Party of the Left, born in 1991 from the old Italian Communist Party, opposed Secretary Achille Occhetto's policy of supporting the prosecutors. Some of the Milanese exponents of the meliorist wing, close to the Socialist Party, were arrested for corruption, but many of them were later discharged.